Apr 02, If lilac bushes are already too large or becoming unsightly, however, pruning the entire bush or tree to about 6 or 8 inches ( cm.) off the ground may be necessary.
Keep in mind that you may have to wait for flowers, as it takes about three years for them to develop once the entire shrub has been cut. When to Trim Lilac Bushes. One possibility- lilacs flower on the growth that occurs after the last flowering- so if you prune in the fall, you’ll be pruning off the branches that would otherwise flower the next spring.
Jul 08, This regular removal of entire old stems will can you trim a lilac bush in the fall your lilac from becoming too tall. Avoid cutting off just the tops of long stems because this can leave the plant with an odd, unnatural shape.
With very large stems, a pruning saw might be necessary. Thick lilac stems can be very tough.
Jun 19, Knowing when to trim older lilac bushes is important. Most lilacs don’t require pruning until they reach about 6 to 8 feet tall. The best time for pruning older lilac bushes is right after their flowering has ceased.
This allows new shoots time to develop the next season of blooms. Pruning too late can kill young developing bushclear.buzzted Reading Time: 3 mins.